1. Field of the Invention
The present invention relates to an image forming apparatus such as a laser printer, LED printer, ink jet printer and the like.
2. Related Background Art
Recently, as personal computers have been remarkably progressed, various printers used as an output device which is one of peripheral equipments for the personal computer have also been popularized. Particularly, printers which operate at a high speed with less noise and provide a high quality image and which are called "page printers", such as laser printers, LED printers, ink jet printers and the like have been remarkably popularized in the recent years.
On the other hand, since the processing speed of the computers has also been increased, the high functional ability and/or multi-functional ability of the printers have been requested. For example, various printers having high additional functions, such as those of network response type, of double-surface printing type, of multi-print type, of the type having greater ejecting ability, or of the type having greater sheet supply variety have been proposed.
However, in the above-mentioned conventional printers, although the multi-function such as the double-surface print and/or multi-print and the high image forming speed have been attained, there arose a problem that it took a long time to treat a recording medium (transfer sheet) in such a manner that an image was formed in the image forming apparatus and the sheet was then ejected from the image forming apparatus, thus increasing the image forming time.
For example, if the double-surface print or the multi-print is effected, since the conventional image forming apparatus had only one set of image formation processing means such as an image bearing member, it was necessary to treat the same single transfer sheet at least twice by the image formation processing means, with the result that the transfer sheet had to be circulated in the image forming apparatus. Accordingly, the travel distance of the transfer sheet in the image forming apparatus was increased, thus extending the image forming time regarding the transfer sheet.